Timer blade arrangement

ABSTRACT

The timer has switches including upper and lower passive blades and an active blade therebetween. The distal end of the lower passive blade has depending spacers which straddle the cam upon which the follower on the distal end of the active blade rides. The spacers reference the lower passive blade off the hub of the drum type program cam. The lower passive blade is provided with a rest or stop for the upper passive blade limiting downward movement of that blade. With precision molding, both passive blades are accurately referenced from the cam hub and the location of the follower which actuates the active blade is precisely located. Accuracy of switching is increased without increased precision in manufacture. Use of two cam tracks permits simultaneous actuation of the active and &#34;passive&#34; blades to effect faster switching. It is possible to provide a &#34;make-make&#34; arrangement instead of the double throw arrangement.

BACKGROUND OF THE INVENTION

In U.S. Pat. No. 3,431,372 there is shown a timer which provided for anew way of mounting the switches which are actuated by the timing cam.This arrangement permitted increased accuracy in switching without anyneed for adjustment after assembly. In this arrangement three wafers inwhich the switch blades are molded are stacked and any interconnectingbetween the blades is accomplished by bussing between the variouslayers. This construction also provided for terminating the switchterminals in two groups, both of which faced the same direction and eachof which permitted plug-in type connectors to be used. The distal endsof the passive blades were referenced by means of a guide block heldbetween the end plates of the timer. The guide block also receivedTeflon coated steel followers which, by reason of the positioning of theguide block, where quite accurately located on the projected diameter ofthe timing cam. The active blade end projected into the follower andaccurate switching was thus attained.

SUMMARY OF THE INVENTION

The construction of FIGS. 1-5 improves over the patented constructionjust described by way of eliminating the guide block and the separatefollower. By molding parts on the ends of the blades, positive locationof the blades with respect to each other and with respect to the cam isinsured. The lower passive blade has spacers which are referencedrelative to the cam hub and thus accommodate any run-out in the hubshape without adversely affecting precision of switching. Thiseliminiates tolerance problems encountered in the prior construction.The construction also increases the accuracy of switching withoutincreasing the precision of manufacture necessary to attain thisincreased accuracy. Furthermore, the friction of the follower in theguide block in the prior construction has been eliminated and, hence,the torque requirement to turn the cam is reduced to one half.

The construction incorporates integral electrical barriers on the bladeassemblies to minimize the risk of arcing between adjacent blades. Allof this has been attained with cost reduction in manufacture and inassembly. A further advantage of the increased accuracy of switchingresides in the fact the step (angle of rotation) for a given size camdrum can be reduced, thus making more steps available and, hence, moreprogram information possible or, on the other side, the angular step canbe maintained as in the past but the drum diameter and, hence, size ofthe overall timer can be reduced.

The basic construction is readily adapted to "flat" timers as shown inFIGS. 6 and 7 while retaining the advantages already mentioned. Further,by providing two cam tracks whereby the "passive" blades are alsoactuated as in FIG. 8 the switching time can be made shorter and permitapplication to "creep" type timers having flat cam or drumconfiguration. The make-make arrangement can readily be incorporated inany of the foregoing.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in fragmentary form portions of a timer having a programcam operating the switches in radially opposed positions.

FIG. 2 is an end view as indicated in FIG. 1 showing the manner in whichthe spacers on the distal end of the blades straddle the cams operatingthe switches.

FIG. 3 is similar to a portion of FIG. 1 but illustrates the activeblade in the mid position, that is with no circuit closed.

FIG. 4 is similar to FIG. 3 but shows the active blade closed on thelower passive blade.

FIG. 5 is an exploded perspective view partly in section furtherillustrating the construction.

FIG. 6 is a simplified plan view showing application of the concept to aflat program cam.

FIG. 7 is a simplified fragmentary view showing the preferred manner ofapplication to the flat cam in FIG. 6.

FIG. 8 is a simplified view showing a double cam track arrangement forfaster switching time.

FIGS. 9-11 show the concept applied to a make-make switchingarrangement.

DESCRIPTION OF PREFERRED EMBODIMENTS

The program cam drum 10 is located between the timer end plates forrotation in a counterclockwise direction as viewed in FIG. 1. In theforeground of FIG. 1 a cam has a maximum elevation portion 12, a midportion 14 and a low portion 16. The switch actuated by this cam has aplastic follower 18 molded on the distal end of active blade 20, theproximal end of which is embedded in a wafer 22 with the end of theblade projecting to provide a terminal 24. The molded wafer 22 is themiddle wafer of the three stacked wafers. The bottom wafer 26 embedspassive blade 28 which has a molded assembly 30 on its distal end. Oneportion of this assembly constitutes a pair of depending spacers 32,32which ride on the hub or inter-cam space of the cam drum 10 so as tostraddle the cam 12,14,16 against which follower 18 is self-biased. Theassembly 30 also includes an electrical barrier 34 projecting upwardlyat one side of the assembly to increase the effective spacing betweenadjacent switch assemblies to minimize arcing between adjacent switches.The assembly 30 also includes a rest or stop 36 which limits thedownward travel of the upper passive blade 38 which is embedded in theupper wafer 40 with its end also projecting to form a terminal 42. Thelower passive blade also runs through the wafer to provide a terminal44.

In the upper portion of FIG. 1 the follower 18 is riding on the highestportion 12 of the cam so as to lift the active blade and bring itscontact 46 into engagement with the contact 48 carried by the upperpassive blade. The high portion of the cam 12 is selected so as to liftthe distal end of the upper blade 38 off of stop 36 (against itsself-bias) to insure good contact pressure. When the cam is indexed abit further to the position shown in FIG. 3, the follower drops down tothe mid portion 14 of the cam and at this point the distal end of theupper blade 38 rests on stop 36 and contact 46 on the active blade hasmoved away from contact 48 on the upper passive blade while contact 50on the active blade has not moved down far enough to engage the contact52 on the lower blade. Therefore, the circuits are open in thisposition. A little further travel of the cam drum to the position shownin FIG. 4 will allow the active blade to closely approach the lowportion 16 in which position the active blade contact 50 engages contact52 on the lower passive blade closing that circuit. Downward movement ofthe lower blade is prevented by the spacers and contact pressure isobtained by the self-bias of the active blade against the lower blade.

Since the spacers 32 on the molded assembly 30 function to position theend of the lower blade and also provide the stop for the upper bladeand, hence, determine the minimum spacing between contacts 48 and 52 onthe upper and lower blades, respectively, accuracy is assured in thisportion. The molded tip including the follower 18 on the active blade isaccurately located and since all of the wafers are stacked and thislocates the root or proximal ends of the blades, accuracy is insuredsimply by proper mounting of the stacked wafers between the timer endplates. Thus it is only necessary to locate the wafers with some degreeof precision and the follower will then be in the proper location andmust be properly located relative to the passive blades.

It will be noted that the generally diametrically oriented surface ofthe follower 18 is on what might be termed the trailing side of thefollower with respect to the direction of rotation of the cam drum. Inthe lower portion of FIG. 1 it will be noted that this condition isstill true and, hence, the upper and lower switches have differentlyshaped followers relative to the overall assembly. This is to insureproper tracking on the cam surfaces.

As can be seen in FIGS. 2 and 5, the blades in the upper assembly (thesame is true in the lower assembly) operate on alternate cam tracks withthe opposed assembly of switches on the other side of the cam drum beingoperated by the other cams. Since the spacers reference off the cam hub,any run-out in the cam circumference is automatically compensated andwill not affect switching accuracy. It will be noted, particularly inFIG. 2, that the spacing between the spacers and the cam is such that itis not possible to orient the blades relative to the cam upon which theyare to operate in such a way that the follower would "miss" the cam,that is,...fall between the cam and an adjacent spacer. The active blademolded follower and the assembly on the lower passive blade arepreferably self-lubricating plastic such as Nylon or filled Nylon. Dueto this factor and the elimination of the friction of the followers inthe guide blocks as in the aforesaid patent, the torque required torotate this assembly is about one half that found in the patentstructure.

In FIG. 5 an additional feature may be noted (it should be noted thatthis figure has no particular reference to the others, beingrepresentative only) in that the active blade in the left of the figureis provided with a laterally projecting arm 54 which includes adepending finger 56. This permits this blade to operate or be operatedby a lever which is, in turn, operated by a subinterval cam. Forexample, this can interconnect a subinterval cam (old in the art) so asto determine when the subinterval switch is effective in conjunctionwith the program cam.

It will be appreciated that not all switches operated by the program camneed be double acting. Thus in some cases the upper passive blade can beomitted.

FIGS. 6 and 7 illustrate the adaptation of this concept to a flatprogram cam or face cam 60 having radially spaced recessed cam tracks62. The switches are positioned in this instance in a generallytangential relationship to the cam tracks with the actuation pointslying on the radius in the interest of accuracy. The passive blades arereference relative to the smooth surface 64 between the recessed camtracks or grooves. Thus the spacer 66 molded on the end of the lowerpassive blade 68 has a rounded bottom designed to contact and ride onthe smooth inter-cam surface 64. The spacer includes the upwardlyprojecting finger portion 70 against which the upper passive blade 72may rest when it is not being contacted by the active blade 74. Theactive blade is provided with a follower 76 which rides in the cam trackor groove 62 and in the illustrated position is in the neutral positionsince it is riding on surface 78. As the cam moves to the left in FIG. 7relative to the follower 76, the surface 80 will lift the active bladeinto contact with the upper blade 72 which will be lifted from the restor finger 70. A little further cam movement will drop the follower intothe deepest portion 82 of the groove 62 permitting the active blade tonow contact the lower blade.

In this arrangement as in the first embodiment the switches in anyassembly will operate on alternate cam tracks while the switch assemblyor array on the opposite side of the cam face will be operated by theother set of alternate cams. Thus in this arrangement essentially thesame construction is provided with the passive blades referenced from asmooth portion of the program member. As in the first embodiment, themolded end fitting on the lower passive blade may include an electricalbarrier 84 to minimize arc over and permit reduction in spacing betweenadjacent switches.

The passive blade in the embodiments thus far described is referencedrelative to the smooth surface (i.e. the hub or intergroove surface) andthe active blade is the only blade which is moved by a cam track. If theprogram cam is operated in an intermittent or step-by-step fashion andthe actual step is fast, the switching time will be fast. If it isdesired to apply the same concept to a creep timer or to a steppingtimer in which more rapid switching time is desirable, it is possible toactuate the normally passive blade along with the active blade. This isillustrated in FIG. 8 where the active blade 86 has a follower 88resting on the cam surface 90. The lower blade 92 has a follower 94resting in cam track 96 and including the upwardly projecting finger 100as well as the electrical barrier 102. Now, then, it will be apparent byreference to the drawings that during the next step the lower blade willbe lifted so the follower rests on surface 104 while at the same timethe active blade will drop off surface 90 down to surface 106. Thus theactive blade moves down while the heretofore passive blade 92 moves up.As the blade 92 moves up, the rest 100 also moves up and the effect isto catch the upper blade 108 on its way down (following movement) whileat the same time allowing the active blade 86 to drop away from theupper blade, thereby breaking the circuit rapidly. Increased switchingspeed can be achieved by this means to permit application of thisconstruction to a creep-type timer whether that timer be the flat orface cam type or the drum type.

In all of the foregoing descriptions the switching action is essentiallySPDT. In some instances it may only be necessary to have the switcharrangement be SPST (using only two blades). There are, however, somesituations where it would be advantageous to provide a make-make actionin the switching sequence. This can be provided by the constructionshown in FIGS. 9, 10, and 11. Here the upper blade 110 is provided withan integral molded spacer 112 which has a curved contact or shoe portionriding on the smooth surface 114 between the cams. The bias of the upperblade 110 will hold the spacer 112 against the smooth surface 114 butdue to the resiliency of the blade, the blade and its follower can beelevated when indicated. The free end of the middle blade 116 is biasedagainst the rest or stop surface 118 on the follower. The lower blade120 is self-biased downwardly so that the follower 122 on the end of theblade will ride in the cam groove as illustrated in these drawings.

In FIG. 9 the lower blade follower 122 is resting in the bottom track ofthe cam groove. There is no contact between the lower blade and themiddle blade and the middle blade cannot contact the upper blade sinceboth the middle and upper blades are restrained from further downwardmovement. When the lower blade follower 122 reaches the surface 124, thelower blade will be lifted into contact with the middle blade 116 andlift that blade slightly from the rest 118 so as to insure a goodcontact pressure. When the follower 122 is now moved up to rest on thehighest cam track portion 126 the lower two blades move in unison toengage the middle blade with the top blade with enough overtravel tolift spacer 112 from the reference surface and thereby obtain propercontact pressure, this completes the make-make sequence. It will beobvious that as rotation of the cam continues, the upper pair ofcontacts can be opened first followed by opening of the second pair ofcontacts or all contacts could be opened substantially at once by havingthe follower 122 drop from the highest elevation 126 to the lowest inone step. While this description has been directed to application of themake-make circuit to a flat cam, it is obvious that this will workequally well in connection with a drum-type program cam.

We claim:
 1. A timer including a program member rotatable about an axisand provided with spaced cams,a switch fixed relative to the programmember for actuation by a cam, said switch including two blades the freeends of which are biased towards the program member, a follower.Iadd.molded .Iaddend.on one of the blades engaging a cam whereby thecam actuates said one blade relative to the other, follower means moldedon the second blade engaging the program member to reference the secondblade relative to the program member .Iadd.and to constrain the secondblade against lateral movement.Iaddend..
 2. A timer according to claim 1in which the switch includes a third blade biased towards the programmember,said follower means including a stop limiting movement of thethird blade towards the program member.
 3. A timer according to claim 2in which said follower means engages a separate cam on the programmember for actuation thereby.
 4. A timer according to claim 1 in whichthe switch includes a third blade,said follower means including a stopengageable by said third blade to limit movement of the third blade. 5.A timer according to claim 4 in which the first blade is actuated by thecam to first engage the third blade and upon continued motion to movethe third blade from said stop into contact with the second blade.
 6. Atimer according to claim 4 in which the follower means engages aseparate cam track on the program member whereby the second and thirdblades are referenced by the separate cam track while the first blade isactuated by the first named cam,said first blade being engageable witheither the second or third blades and the blades moving into or out ofcontact may be moved in the desired direction simultaneously to increasethe speed of switching.
 7. A timer including a program member providedwith spaced cams for operating switches and means for rotating theprogram member,a plurality of switches fixed relative to the programmember for actuation by respective cams, each of the switches includinga blade having its proximal end fixed and its distal end including acontact and spacer means .Iadd.molded on the blade and .Iaddend.engagingthe program member so as to reference the contact relative to theprogram member .Iadd.and to constrain the blade against lateralmovement.Iaddend., a second blade having its proximal end fixed relativeto the first blade with its distal end including a contact and adepending follower .Iadd.molded on the blade and .Iaddend.engaging oneof the cams on the program member, the second blade being self-biased tourge the follower into engagement with the cam whereby the second bladeis actuated in accordance with the configuration of the cam to open andclose said contacts in a programmed sequence.
 8. The construction ofclaim 7 including means confining the follower on the second bladeagainst lateral movement whereby the follower is kept on its associatedcam.
 9. A timer according to claim 7 in which the program member is flatand said cams are concentric about the center of rotation of the programmember,said switches being disposed in generally tangential relationshipto the cams.
 10. A timer according to claim 7 in which the programmember is cylindrical with the cams axially spaced along the cylinderand the switches are disposed in generally tangential relationship tothe cylinder.
 11. Apparatus according to claim 7 in which said spacermeans engages another cam on the program member whereby both blades maybe actuated by their respective cams.
 12. Apparatus according to claim 7including an electrical barrier projecting from one of the bladesbetween it and the adjacent blades of the adjacent switch a sufficientheight to electrically shield the contacts associated with the firstswitch from the adjacent contacts.
 13. Apparatus according to claim 7 inwhich the distal end of the first blade is provided with an upwardlyprojecting stop,a third blade having its proximal end fixed relative tothe first and second blades and having its distal end overlying saidstop and having a contact adapted to be engaged by the second bladecontact, said third blade being self-biased against said stop andmovable upwardly therefrom in response to elevation of the second bladeby the cam to close the second blade contact on the upper blade contact.14. A timer according to claim 7 in which the follower on the secondblade is generally disposed on the projected diameter of said programmember.
 15. A timer including a program member having spaced cams,anassembly of spaced switches fixed relative to the program member foractuation by the cams, each of said switches including a blade havingits free end self-biased towards said program member and including aspacer .Iadd.molded on the blade and .Iaddend.acting on the programmember to reference the blade relative thereto, second blade operativelyassociated with the first blade in a switch and having a dependingfollower .Iadd.molded on the blade and .Iaddend.biased into contact withthe associated cam, contacts on said blades which are opened and closedaccording to the configuration of the associated cam.
 16. A timeraccording to claim 15 in which said spacer is part of an assembly moldedon the end of the first blade, said assembly including an electricallyinsulative barrier disposed between the contacts of said switch and thecontacts of an adjacent switch.
 17. A timer according to claim 15 inwhich each said second blade follower engages its associated cam betweenmeans limiting lateral movement of the follower.